1. Field of the Invention
The invention relates to the method of assaying of gold or other metals which uses a smooth black stone such as an Arkansas stone on which markings are applied. In particular, the invention relates to the means for holding the gold needles which are used in conjunction with this method.
2. Description of the Prior Art
In the known assaying method, a gold needle of known karat is first rubbed on the stone to create a streak. An unnoticeable part to the piece to be tested is used to make a mark next to the first mark. A streak of acid of known strength is then drawn across the two gold streaks, and observed to see which mark burns away first. This mark is of the lower karat so that if the mark of unknown karat burns away first, another needle of lower known carat may be selected and the test rerun until it is determined that the piece being tested is between two known carats. A prior art device for holding the test needles comprises a ring carrying a group of independently movable needle supports, each support comprising a tapered copper member to the outer end of which the gold needle of known carat is silver soldered. A problem with this conventional needle holding device is that the assaying equipment is usually kept in a closed box together with the testing stone and acid containers, and the acid fumes have a tendency to break down the silver soldered connections. The gold needles are thus apt to break off from the copper supports. If even one needle is lost, the entire tool and assaying kit becomes useless for its intended purpose.